Paper

How Products Are Made
COPYRIGHT 1996 Gale Research Inc.

Paper

Background

Formed from wood pulp or plant fiber, paper is chiefly used for written communication. The earliest paper was papyrus, made from reeds by the ancient Egyptians. Paper was made by the Chinese in the second century, probably by a Chinese court official named Cai Lun. His paper was made from such things as tree bark and old fish netting. Recognized almost immediately as a valuable secret, it was 500 years before the Japanese acquired knowledge of the method. Papermaking was known in the Islamic world from the end of the eighth century a.d.

Knowledge of papermaking eventually moved westward, and the first European paper mill was built at Jativa, in the province of Valencia, Spain, in about 1150. By the end of the 15th century, paper mills existed in Italy, France, Germany, and England, and by the end of the 16th century, paper was being made throughout Europe.

Paper, whether produced in the modern factory or by the most careful, delicate hand methods, is made up of connected fibers. The fibers can come from a number of sources including cloth rags, cellulose fibers from plants, and, most notably, trees. The use of cloth in the process has always produced high-quality paper. Today, a large proportion of cotton and linen fibers in the mix create many excellent papers for special uses, from wedding invitation paper stock to special paper for pen and ink drawings.

The method of making paper is essentially a simple one—mix up vegetable fibers, and cook them in hot water until the fibers are soft but not dissolved. The hot water also contains a base chemical such as lye, which softens the fibers as they are cooking. Then, pass a screen-like material through the mixture, let the water drip off and/or evaporate, and then squeeze or blot out additional water. A layer of paper is left behind. Essential to the process are the fibers, which are never totally destroyed, and, when mixed and softened, form an interlaced pattern within the paper itself. Modern papermaking methods, although significantly more complicated than the older ways, are developmental improvements rather than entirely new methods of making paper.

Raw Materials

Probably half of the fiber used for paper today comes from wood that has been purposely harvested. The remaining material comes from wood fiber from sawmills, recycled newspaper, some vegetable matter, and recycled cloth. Coniferous trees, such as spruce and fir, used to be preferred for papermaking because the cellulose fibers in the pulp of these species are longer, therefore making for stronger paper. These trees are called "softwood" by the paper industry. Deciduous trees (leafy trees such as poplar and elm) are called "hardwood." Because of increasing demand for paper, and improvements in pulp processing technology, almost any species of tree can now be harvested for paper.

Some plants other than trees are suitable for paper-making. In areas without significant forests, bamboo has been used for paper pulp, as has straw and sugarcane. Flax,
hemp, and jute fibers are commonly used for textiles and rope making, but they can also be used for paper. Some high-grade cigarette paper is made from flax.

Cotton and linen rags are used in fine-grade papers such as letterhead and resume paper, and for bank notes and security certificates. The rags are usually cuttings and waste from textile and garment mills. The rags must be cut and cleaned, boiled, and beaten before they can be used by the paper mill.

Other materials used in paper manufacture include bleaches and dyes, fillers such as chalk, clay, or titanium oxide, and sizings such as rosin, gum, and starch.

The ManufacturingProcess

Making pulp

1 Several processes are commonly used to convert logs to wood pulp. In the mechanical process, logs are first tumbled in drums to remove the bark. The logs are then sent to grinders, which break the wood down into pulp by pressing it between huge revolving slabs. The pulp is filtered to remove foreign objects. In the chemical process, wood chips from de-barked logs are cooked in a chemical solution. This is done in huge vats called digesters. The chips are fed into the digester, and then boiled at high pressure in a solution of
sodium hydroxide and sodium sulfide. The chips dissolve into pulp in the solution. Next the pulp is sent through filters. Bleach may be added at this stage, or colorings. The pulp is sent to the paper plant.

Beating

2 The pulp is next put through a pounding and squeezing process called, appropriately enough, beating. Inside a large tub, the pulp is subjected to the effect of machine beaters. At this point, various filler materials can be added such as chalks, clays, or chemicals such as titanium oxide. These additives will influence the opacity and other qualities of the final product. Sizings are also added at this point. Sizing affects the way the paper will react with various inks. Without any sizing at all, a paper will be too absorbent for most uses except as a desk blotter. A sizing such as starch makes the paper resistant to water-based ink (inks actually sit on top of a sheet of paper, rather than sinking in). A variety of sizings, generally rosins and gums, is available depending on the eventual use of the paper. Paper that will receive a printed design, such as gift wrapping, requires a particular formula of sizing that will make the paper accept the printing properly.

Pulp to paper

3 In order to finally turn the pulp into paper, the pulp is fed or pumped into
giant, automated machines. One common type is called the Fourdrinier machine, which was invented in England in 1807. Pulp is fed into the Fourdrinier machine on a moving belt of fine mesh screening. The pulp is squeezed through a series of rollers, while suction devices below the belt drain off water. If the paper is to receive a water-mark, a device called a dandy moves across the sheet of pulp and presses a design into it.

The paper then moves onto the press section of the machine, where it is pressed between rollers of wool felt. The paper then passes over a series of steam-heated cylinders to remove the remaining water. A large machine may have from 40 to 70 drying cylinders.

Finishing

4 Finally, the dried paper is wound onto large reels, where it will be further processed depending on its ultimate use. Paper is smoothed and compacted further by passing through metal rollers called calendars. A particular finish, whether soft and dull or hard and shiny, can be imparted by the calendars.

The paper may be further finished by passing through a vat of sizing material. It may also receive a coating, which is either brushed on or rolled on. Coating adds chemicals or pigments to the paper's surface, supplementing the sizings and fillers from earlier in the process. Fine clay is often used as a coating. The paper may next be supercalendered, that is, run through extremely smooth calendar rollers, for a final time. Then the paper is cut to the desired size.

Environmental Concerns

The number of trees and other vegetation cut down in order to make paper is enormous. Paper companies insist that they plant as many new trees as they cut down. Environmentalists contend that the new growth trees, so much younger and smaller than what was removed, cannot replace the value of older trees. Efforts to recycle used paper (especially newspapers) have been effective in at least partially mitigating the need for destruction of woodlands, and recycled paper is now an important ingredient in many types of paper production.

The chemicals used in paper manufacture, including dyes, inks, bleach, and sizing, can also be harmful to the environment when they are released into water supplies and nearby land after use. The industry has, sometimes with government prompting, cleared up a large amount of pollution, and federal requirements now demand pollutionfree paper production. The cost of such clean-up efforts is passed on to the consumer.

Paper

UXL Encyclopedia of Science
COPYRIGHT 2002 The Gale Group, Inc.

Paper

Paper is an indispensable part of everyday life. Beyond its use as the basic material for written and printed communication, paper in its various forms are used for hundreds of other purposes, including packaging, wrapping, insulating, and toweling. Each year, Americans use an average of 750 pounds (340 kilograms) of paper products per person. That equates to 210 billion pounds (95 billion kilograms) of paper products used in the United States per year.

The word paper comes from papyrus, a reedy plant that used to grow abundantly along the Nile River in Egypt. Centuries ago, ancient Egyptians removed the fibrous layers from the stem of this plant and cemented them together to create a durable woven writing material also known as papyrus. Examples of papyrus manuscripts have survived to the present.

Many sources claim that paper (as we know it) was first invented in a.d. 105 by Ts'ai Lun, a Chinese court official. Historians believe he mixed mulberry bark, hemp, and rags with water, mashed it into a pulp, pressed out the liquid, then hung the thin mat on a mold of bamboo strips to dry in the Sun. Paper made from rags in about a.d. 150 still exists today.

By the early seventh century, paper and its production had been introduced into Japan. From here, it spread to Central Asia by 750. Paper did not make its way into Europe until about 1150, but it spread throughout the continent over the next few centuries. Rags were the chief source of paper fibers until the introduction of papermaking machinery in the early nineteenth century, when it became possible to obtain papermaking fibers from wood.

Words to Know

Calendar rolls: Highly polished metal rollers used to compact and smooth paper after it has dried.

Cellulose: An insoluble carbohydrate that plants use as building material to make their cell walls.

Deckle: Frame around the edges of a mold used to make paper by hand; also, either of the straps around the edge of the screening of a papermaking machine.

Fourdrinier machine: Machine that forms paper from pulp, named after the English brothers who financed its development in the early nineteenth century.

Today, paper can be both handmade and machine-made. Both types of paper consist of tiny cellulose fibers pressed together in a thin sheet. Each of these fibers is a tiny tube, about 100 times as long as it is wide. Today, most fibers come from wood, though in earlier times, the source was more likely to have been rags of linen or cotton. The source material is reduced to a slurry of fibers that float freely in water, and many of the fibers will have been broken or cut when making the pulp. When the water is removed, the fibers form a thin layer of pulp that eventually becomes paper.

Handmade paper

Rags to be made into paper are first sorted, and any unsuitable ones are discarded. Seams are opened and items such as buttons are removed. The rags are chopped into small pieces, which are then boiled in strong cleansing solutions. Next, the pieces are rinsed and beaten while damp until all of the threads have disintegrated and the fibers float freely in water. This is the paper pulp.

The very dilute pulp is next sent to the vat where the paper will actually be made. A rectangular mold containing wires running at right angles to each other is used to make a film of the pulp. Traditional molds have thin, closely spaced parallel wires running across the mold at the surface. These are attached to thick, widely spaced wires beneath them that run perpendicular or in the opposite direction. Paper formed on this type of mold typically reveals a ladder-like pattern when held up to the light, and is known as laid paper. Woven paper is formed on a mold of plain, woven wire screening. Thin wire forming a design may be attached to the mold's surface wires to produce a watermark in the finished paper. A rectangular frame, called the deckle, is placed over the mold to convert the mold into a sort of tray.

The papermaker then dips the mold with the deckle attached into the vat of dilute pulp and draws up a small amount of pulp on the surface of the wire. The mold is then shaken and tilted until most of the water has drained through the wire. The deckle is removed, and additional water is allowed to drain off. A second worker takes the mold and transfers the film of pulp to a piece of damp felt, laying a second piece of felt across the top.

This process continues until a stack of alternating wet paper and felt has built up. The stack is placed in a press to eliminate any residual

water. Then the paper and felt are separated, and the paper is pressed by itself and hung up to dry. When dry, the paper sheets are dipped in a tub containing gelatin or very dilute glue and dried again. This gives the paper a harder and less absorbent finish than it would otherwise have had.

All paper was made by hand until the early nineteenth century. Artists use most of the handmade paper produced today, although many other people believe it to be the finest printing surface available.

Machine-made paper

Hardly any paper for book printing is made from rags today. Wood is the main ingredient of paper pulp, though the better papers contain cotton fiber, and the best are made entirely of cotton. The fibers are converted into pulp by chemical or mechanical means. Chemical pulp is used to make fine white paper, whereas mechanical pulp is used to make newsprint, tissue, towel, and other inexpensive papers.

Chemical pulp begins with the debarking of logs. Chippers with whirling blades reduce the logs to smaller and smaller chips. The wood chips are then boiled in a large vat called a digester that contains strong caustic solutions that dissolve away parts of the wood that are not cellulose. This leaves only pure fibers of cellulose.

Mechanical pulp also begins with debarked logs. The logs are then ground up into fibers by a rapidly revolving grindstone. Spruce, balsam, and hemlock are the woods considered best suited for pulping by this process. Unlike chemical pulp, mechanical pulp contains all of the parts of the original wood. Because of this, mechanical pulp is weak and tends to discolor quickly. If mechanical pulp is to be used to make white paper, it is usually bleached with chlorine dioxide or sodium hydroxide. Paper pulp used to be bleached with chlorine, but the U.S. Environmental Protection Agency (EPA) determined that the process of bleaching paper with chlorine produces dioxin, a carcinogen or cancer-causing agent. In 1998, the EPA mandated that paper companies switch to safer compounds

The machine that converts either type of pulp into paper is called a fourdrinier machine, after English brothers Henry and Sealy Fourdrinier, who financed its development in 1803. The fourdrinier machine takes pulp that is almost 100 percent water and, by removing almost all the water, changes it into a continuous web of paper.

Watery pulp enters the fourdrinier machine on an endless moving belt of nylon mesh screening. As it moves forward, the screening is agitated from side to side to drain the excess water. Deckle straps prevent the liquid pulp from slopping over the sides. Air suction pumps beneath the screening also pull more water through. As the pulp passes along on the belt, a turning cylinder presses on it from above. This cylinder, called a dandy roll, is covered with wire mesh that imparts either a wove or a laid surface to pulp, depending on the pattern of the mesh.

At the end of the fourdrinier machine is a series of felt-covered rollers. As the pulp (now very wet paper) passes through them, they press still more water out of it, condensing the fibers. The paper then passes through sets of smooth metal press rollers that give a smooth finish to both surfaces of the paper. The drying process is completed after the fully formed paper passes through a series of large heated rollers. Once dried, the paper undergoes calendaring, in which it is pressed between a series of smooth metal (calendar) rollers that give it a polished surface. Afterward, the paper is cut into sheets or wrapped into a roll.

Cite this article Pick a style below, and copy the text for your bibliography.

paper

The Columbia Encyclopedia, 6th ed.

Copyright The Columbia University Press

paper, thin, flat sheet or tissue made usually from plant fiber but also from rags and other fibrous materials. It is used principally for printing and writing on but has many other applications. The term also includes various types of paperboard, such as cardboard and wallboard.

The Formulation of Paper

A quarter to a third of most new paper is made from waste paper. The body of paper is made up of matted cellulose fibers—since c.1860 derived principally from wood. Rags, mostly cotton cuttings from textile and garment factories, are used to make fine stationery and for such purposes as cigarette paper. For other special papers, or where wood is not available, manufacturers may use pressed sugarcane, bamboo, manila rope, cereal straws, esparto grass, or other fibers.

Preparation from Wood Pulp

Most paper is made from wood pulp. Mechanical pulp, or groundwood, prepared by grinding the wood, is used to make newsprint, tissue, towel, and other inexpensive papers. For paper whose whiteness is important, a chemical pulp must be prepared. Lignin, which holds wood fibers together, turns yellow in sunlight and therefore must be removed by alternating treatments with acid and alkaline solutions. The wood pulp, boiled under pressure and treated to dissolve the lignin binder, is thus turned into cellulose fiber. The mixture is then washed and bleached; because the resulting pulp is more than 90% water, the water is usually treated before mixing.

Once the wood pulp has been treated, washed, bleached, screened, and beaten, it is blended to achieve the characteristics required for the intended use. The pulp, suspended in water, is poured over a wire screen in one of two machines that differ mainly in the form of the screen: a belt screen is used in the Fourdrinier machine and a cylindrical one in the cylinder machine. As water drains through the screen, a layer of fibers forms, which in the Fourdrinier is shaken to turn the fibers in different directions so that they mat. A wet felt belt pressed against the screen picks up the paper for feeding through sets of drying rollers. During this stage a rubber roller may be used to imprint a watermark. At the end of the process the paper is passed through a calender (stack of iron rollers), which presses the paper and smooths its surface. Fillers—chiefly clay or starch—are used to improve the printing, texture, and wet and dry strength of paper and to produce other special properties.

Treatment for Special Properties

Book paper is any kind of printing paper except newsprint; in order to prevent rapid deterioration of the paper through a reaction between the acids in the pulp mixture and the humidity in the air, modern book paper is further treated to make it acid-free. For the best reproduction of illustrations, especially halftones, book paper is coated with a layer of mineral pigment, usually clay, mixed with an adhesive. All writing papers are
"sized"
; i.e., a water-resistant substance such as rosin is added to the pulp to prevent the spreading of writing ink. Hanging paper, or wallpaper, is soft and bulky; it is rosin-sized for water resistance and coated to take a printed design. Bag and wrapping papers are made of kraft paper, the product of the sulfate process, because of its strength.

The Introduction of Paper

Paper is believed to have been invented by Ts'ai Lun c.105 in China, where it reached an advanced state of development. Chinese paper was a mixture of bark and hemp. Papermaking spread to Japan c.610 and to Samarkand c.751, whence it was introduced by the Arabs into Egypt c.900 and by the Moors into Spain at Játiva c.1150. Mills were established in Italy c.1276; in France, c.1348; in Germany, 1390; and in England, 1495. European paper was usually made of flax and hemp. Primitive bark paper had been made in Mexico and Central America in pre-Columbian times. Paper was first produced in the American colonies in 1690 by William Rittenhouse at Germantown.

paper

pa·per
/ ˈpāpər/
•
n.
1.
material manufactured in thin sheets from the pulp of wood or other fibrous substances, used for writing, drawing, or printing on, or as wrapping material:
a sheet of paper |
[as adj.]
a paper bag. ∎
a newspaper.
∎
wallpaper.
∎ (usu. papers)
a piece or sheet of paper with something written or drawn on it:
he riffled through the papers on his desk. ∎ (papers)
significant or important documents belonging to a person:
the personal papers of major political figures. ∎ [as adj.]
denoting something that is officially documented but has no real existence or little merit or use:
a paper profit. ∎
a government report or policy document:
a recently leaked cabinet paper. ∎ (papers)
documents attesting identity; credentials:
two men stopped us and asked us for our papers. ∎
a piece of paper used for wrapping or enclosing something or made into a packet:
toffee papers. ∎
short for commercial paper.
∎ short for cigarette paper.
2.
an essay or thesis, esp. one read at an academic lecture or seminar or published in an academic journal.
3. theatrical slang
free passes of admission to a theater or other entertainment.
•
v. [tr.]
1. (often be papered)
apply wallpaper to (a wall or room):
the walls were papered in a Regency stripe. ∎ [intr.] (paper over)
cover (a hole or blemish) with wallpaper.
∎ (paper over)
disguise (an awkward problem) instead of resolving it:
the ill feeling between her and Jenny must have been papered over.2. theatrical slang
fill (a theater) by giving out free tickets.
PHRASES:be not worth the paper it is written on
be of no value or validity whatsoever despite having been written down.make the papers
be written about in newspapers and thus become famous or notorious.on paper
in writing.
∎
in theory rather than in reality:
the combatants were, on paper at least, evenly matched.DERIVATIVES:pa·per·er
n.pa·per·less
adj.

Cite this article Pick a style below, and copy the text for your bibliography.

Paper

Plant Sciences
COPYRIGHT 2001 The Gale Group Inc.

Paper

Paper is a flexible web or mat of pulp fibers of plant (usually wood) origin. It is widely used for printing, packaging, and sanitary applications and also has a wide variety of specialized uses. Paper is formed from a dilute aqueous slurry of pulp fibers, fillers, and additives. Fillers are inert materials such as calcium carbonate, clay, and titanium dioxide that make printing papers whiter and increase opacity (the ability to read print on one side of the paper without print on the other side of the paper showing through). Additives are materials used to improve the papermaking process and modify the final product. Additives include dyes, strength agents, and sizing agents (used to make paper resistant to water penetration).

Pulp is obtained by mechanical or chemical means or by a combination of the two. The two most common pulping methods are thermomechanical pulping and kraft chemical pulping. Thermomechanical pulp accounts for about 20 percent of pulp production in North America. The process consists of introducing wood chips between two large metal discs (on the order of 2 meters in diameter) that have raised bars on their surfaces and that rotate in opposite directions. The discs are in a pressurized refiner that operates at a temperature of 130°C. The combination of mechanical action and steam forms a wood pulp. This wood pulp retains the original lignin of the wood so the paper made from it is not very strong and yellows with age. Mechanical pulp is the chief component of newsprint.

Kraft pulp is formed by cooking wood chips in a highly alkaline aqueous solution at 170°C. It accounts for about 70 percent of pulp production in North America. In this process most of the lignin is removed. The brown pulp is used in sack paper and for the production of corrugated boxes. The bleached pulp is used in white printing papers and tissue papers.

Wood fiber accounts for about 98 percent of pulp production in North America, while globally it accounts for about 92 percent of pulp production. About two-thirds of the wood comes from softwoods because their high fiber length (3 to 5 millimeters) produces strong paper. The short fibers of hardwood species (approximately 1 millimeter) are used with softwood fibers in printing papers to achieve high strength and surface smoothness. Major nonwood sources of fiber, in decreasing levels of global production, include straw (especially wheat), sugarcane residue, bamboo, reeds, and cotton linters. Hemp fibers can also be used, but their fibers are so long that they must be cut in order to make paper from them.

The paper machine continuously forms, drains water, presses, and dries the web of paper fibers, using a single continuously moving plastic screen. The pulp slurry that is applied to the wire consists of 3 to 6 kilograms of dry fiber per 1,000 kilograms of water. Water is then removed by gravity, vacuum, pressing rolls, and, finally, heat in the drier section of the machine.
Twin wire machines form the web between two plastic screens, and cylinder machines form several layers of paper that are combined to form heavyweight boards. Paper is converted to a wide variety of products in operations that may include trimming, rewinding onto smaller rolls, cutting into sheets, coating, printing, and box making.

paper

paper Sheet or roll of compacted cellulose fibres with a wide range of uses. The word ‘paper’ derives from papyrus, the plant that the Egyptians used more than 5500 years ago to make sheets of writing material. The modern process of manufacture originated c.2000 years ago in China, and consists of reducing wood fibre, straw, rags or grasses to a pulp by the action of an alkali, such as caustic soda. The non-cellulose material is then extracted and the residue is bleached. After washing and the addition of a filler to provide a smooth and flat surface, the pulp is made into thin sheets and dried. These can be coated to produce a special surface, such as glossy paper for photographs.

Cite this article Pick a style below, and copy the text for your bibliography.

Paper

West's Encyclopedia of American Law
COPYRIGHT 2005 The Gale Group, Inc.

PAPER

A document that is filed or introduced in evidence in a lawsuit, as in the phrases papers in the case and papers on appeal.

Any written or printed statement, including letters, memoranda, legal or business documents, and books of account, in the context of thefourth amendmentto the U.S. Constitution, which protects the people from unreasonablesearches and seizureswith respect to their "papers" as well as their persons and houses.

In the context of accommodation paper andcommercial paper, a written or printed evidence of debt.

Cite this article Pick a style below, and copy the text for your bibliography.

paper

paper not worth the paper it is written on of no value or validity despite having been written down.paper over the cracks use a temporary expedient, or to create a mere semblance of order. The phrase is a translation of a German expression used by Otto von Bismarck in a letter of 1865, and early uses refer to this.paper tiger a person or thing that appears threatening but is ineffectual. The expression became well-known in the West from its use by Mao Zhe Dong in an interview in 1946.

Cite this article Pick a style below, and copy the text for your bibliography.